Unsaturated diphosphine monoxides

ABSTRACT

The present invention relates to unsaturated diphosphine monoxides, to a process for preparation thereof and to the use thereof as flame retardants.

The present invention relates to unsaturated diphosphine monoxides, to a process for preparation thereof and to the use thereof as flame retardants.

There is a drive to replace halogenated flame retardants with corresponding halogen-free flame retardants. It is particularly advantageous when the flame retardant can be mixed not just physically into the material to be protected, but also bonds to its structure and thus cannot be removed from the material by physical processes. There is a great need for unsaturated diphosphine monoxides which can also be incorporated into polymerizable plastics as flame retardants. The present application describes the diphosphine monoxides which comprise unsaturated C—C bonds.

Inorg. Nucl. Chem. Letters, 1967, Vol. 3, on page 313, describes the reaction of dialkyl- or diphenylphosphine chloride with trimethoxyphosphine or with methoxydiphenylphosphine to give the corresponding diphosphine monoxide according to the scheme below.

The disadvantage of the obtainable dialkoxy derivatives and of tetraphenyldiphosphine monoxide is that they cannot be incorporated chemically into the polymerizable network of the plastic.

It is therefore an object of the present invention to provide compounds which are firstly halogen-free, secondly can be incorporated chemically into a polymer matrix and thirdly have outstanding flame retardancy properties.

This object is achieved by compounds of the formula I

where the R1-R2 radicals are each independently selected from the group of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₁-C₁₆-alkoxy, C₁-C₁₆-alkenyloxy, C₃-C₁₀-cycloalkyl, C₃-C₁₀-cycloalkoxy, C₆-C₁₀-aryl, C₆-C₁₀-aryloxy, C₆-C₁₀-aryl-C₁-C₁₆-alkyl, C₆-C₁₀-aryl-C₁-C₁₆-alkoxy, NR²R³, COR², COOR² and CONR²R³, the R³ radical is a substituted or unsubstituted, heteroatom-comprising or non-heteroatom-comprising, organic hydrocarbon group which comprises at least one double bond, and R⁴ is selected from the group of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₁-C₁₆-alkenyloxy, C₁-C₁₆-alkoxy, C₁-C₁₆-alkyl-NR²R³, C₃-C₁₀-cycloalkyl, C₃-C₁₀-cycloalkoxy, C₆-C₁₀-aryl, C₆-C₁₀-aryloxy, C₆-C₁₀-aryl-C₁-C₁₆-alkyl, C₆-C₁₀-aryl-C₁-C₁₆-alkoxy, NR²R³, COR², COOR² and CONR²R³, preference being given to C₁-C₁₆-alkyl and C₆-C₁₀-aryl groups.

The inventive compounds are advantageous when OR³ and R⁴ in the compound of the formula I are identical.

The inventive compounds are advantageous when R³ and R⁴ in the compound of the formula I are allyloxy groups.

The present invention further provides a process for preparing the compounds of the formula I according to any one of claims 1 to 3, comprising the following steps

-   -   a) reacting a compound of the formula II

-   -   b) with the compound of the formula III

-   -   where the R⁵ radical is selected from the group of C₁-C₁₆-alkyl,         C₁-C₁₆-alkenyl, C₃-C₁₀-cycloalkyl and C₆-C₁₀-aryl.

The process according to the invention is advantageous when the reaction of the compound of the formula II with the compound of the formula III is carried out at temperatures of from 0° C. to 150° C.

The invention further provides for the use of the compounds of the formula I as flame retardants in plastics.

The R¹-R² radicals are each independently selected from the group of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₁-C₁₆-alkoxy, C₁-C₁₆-alkenyloxy, C₃-C₁₀-cycloalkyl, C₃-C₁₀-cycloalkoxy, C₆-C₁₀-aryl, C₆-C₁₀-aryloxy, C₆-C₁₀-aryl-C₁-C₁₆-alkyl, C₆-C₁₀-aryl-C₁-C₁₆-alkoxy, NR²R³, COR², COOR² and CONR²R³. Preferred C₁-C₁₆-alkyl groups are methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, i-butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, 2-ethylhexyl and 2-propylheptyl.

Preferred C₆-C₁₀-aryl groups are phenyl and naphthyl. Particular preference is given to phenyl.

It is very particularly preferred when the R¹ and R² radicals are identical. The phenyl group is very especially preferred for R¹ and R².

The R³ radical is a substituted or unsubstituted, heteroatom-comprising or non-heteroatom-comprising, organic hydrocarbon group which comprises at least one double bond. R³ is preferably selected from the group of vinyl, allyl, 2-vinyloxyethyl, 2-vinyloxyethyloxyethyl and other ethoxylated oligomers. The allyl group is very particularly preferred for R³.

The R⁴ radical is selected from the group of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₁-C₁₆-alkenyloxy, C₁-C₁₆-alkoxy, C₁-C₁₆-alkyl-NR²R³, C₃-C₁₀-cycloalkyl, C₃-C₁₀-cycloalkoxy, C₆-C₁₀-aryl, C₆-C₁₀-aryloxy, C₆-C₁₀-aryl-C₁-C₁₆-alkyl, C₆-C₁₀-aryl-C₁-C₁₆-alkoxy, NR²R³, COR², COOR² and CONR²R³, preference being given to C₁-C₁₆-alkyl and C₆-C₁₀-aryl groups.

Particularly preferred compounds are those in which the R¹ and R² radicals and the OR³ and R⁴ radicals are identical. Very particular preference is given to compounds in which R¹ and R² are each C₆-C₁₀ aryl groups, especially phenyl groups, and OR³ and R⁴ are each alkenyloxy groups, especially allyloxy groups.

The R⁵ radicalin the process according to the invention is identical to R¹, R², R³ or R⁴. R⁵ is preferably identical to R³. Allyl is especially preferred.

The inventive compounds of the formula I are prepared by reacting the compounds of the formula II with those of the formula III.

The reaction of the compounds of the formula II with III can be carried out in the presence of solvents. Preferred solvents are aromatic solvents selected from the group of toluene, xylene and mesitylene. The reaction is performed preferably at temperatures in the range from 0 to 150° C., more preferably in the range from 20 to 120° C. and most preferably in the range from 20 to 30° C. The solvent is removed after the reaction has ended. The solvent can be removed by any method of removal known to those skilled in the art. Preference is given to distilling. The resulting product is then dried. Preference is given to drying under a reduced pressure in the range from 300 to 3 mbar.

The resulting product can be used as a flame retardant in different plastics, by virtue of the inventive product being bound to the polymeric backbone by copolymerization or blended with the plastic by compounding.

EXAMPLE Preparation of 1,1-diphenyl-2,2-diallyloxydiphosphine monoxide

Triallyl phosphite (101 g, 0.5 mol) in toluene (500 ml) is initially charged in a round bottom flask. Within 1 h, chlorodiphenylphosphine (110.5 g, 0.5 mol) is added dropwise at 25° C. The mixture is stirred under reflux for a further 7 hours and then cooled. Toluene is distilled off over a Claisen apparatus at 60° C. and 1 mbar. The product is dried under oil-pump vacuum. The product (147 g, 85% yield) is obtained as a clear yellow liquid of purity>80% (³¹P NMR). ³¹P NMR (toluene-D8): −31.1 (d, ¹J 204 Hz); 34.1 (d, ¹J 204 Hz). 

The invention claimed is:
 1. A compound of the formula I

where the R1-R2 radicals are each independently selected from the group consisting of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₁-C₁₆-alkoxy, C₁-C₁₆-alkenyloxy, C₃-C₁₀-cycloalkyl, C₃-C₁₀-cycloalkoxy, C₆-C₁₀-aryl, C₆-C₁₀-aryloxy, C₆-C₁₀-aryl-C₁-C₁₆-alkoxy, NR²R3, COR², COOR² and CONR²R³, the R³ radical is an allyl group and R⁴ is an allyloxy group.
 2. A process for preparing the compounds of the formula 1 according to claim 1, comprising a) reacting a compound of the formula II

b) with the compound of the formula III

where the R⁵ radical is selected from the group consisting of C₁-C₁₆-alkyl, C₁-C₁₆-alkenyl, C₃-C₁₀-cycloalkyl and C₆-C₁₀-aryl.
 3. The process according to claim 2, wherein the reaction of the compound of the formula II with the compound of the formula III is carried out at temperatures of from 0° C. to 150° C.
 4. A flame retardant, comprising the compound of formula I according to claim
 1. 5. The compound of claim 1, wherein R¹ and R² are phenyl.
 6. The flame retardant according to claim 4, which is suitable as a flame retardant in plastics. 